Can't have it both ways. Either the heavier weight offers more protection by staying with a part longer and retaining more heat or it does not offer any additional protection because it leaves the part as quickly.
I never stated a head gasket can be lost by any oil. What I did say were passages could be coked by the wrong viscosity. Some manufacturers have refused warranty claims on the top
end by testing the engine oil the user was running, Ford for one with early 90's escorts, Chev w/ C4 vettes and Dodge and the 2nd gen Viper.
Oil is much like religion some are basing their choices or use based on faith and not empirical evidence. Personally I run oils based on manufacturers recommendations and specifications except on the bikes where I have some oils work better based on my testing. To each their own.